Measuring the attack surfaces of two FTP daemons

Software consumers often need to choose between different software that provide the same functionality. Today, security is a quality that many consumers, especially system administrators, care about and will use in choosing one software system over another. An attack surface metric is a security metric for comparing the relative security of similar software systems 8. The measure of a systems attack surface is an indicator of the systems security: given two systems, we compare their attack surface measurements to decide whether one is more secure than another along each of the following three dimensions: methods, channels, and data. In this paper, we use the attack surface metric to measure the attack surfaces of two open source FTP daemons: ProFTPD 1.2.10 and Wu-FTPD 2.6.2. Our measurements show that ProFTPD is more secure along the method dimension, ProFTPD is as secure as Wu-FTPD along the channel dimension, and Wu-FTPD is more secure along the data dimension. We also demonstrate how software consumers can use the attack surface metric in making a choice between the two FTP daemons.